Recent studies show that bone marrow-derived stem cells differentiate into microglia, astrocytes, and neurons. A variety of preparations, including crude bone marrow, marrow stromal cells, and hematopoietic stem cells have been used for transplantation into animal models. Brain injury may enhance this differentiation. We plan to compare the potential of different bone marrow preparations to differentiate into brain cells in a mouse model of neonatal hypoxic-ischemic (HI) injury. Our hypothesis is that undifferentiated bone marrow assists in recovery from this injury by the contribution of cells which differentiate into cerebral endothelial cells, astrocytes, oligodendrocytes, and neurons. Our specific aims are: 1) determine the expression of neural and endothelial markers in cells arising from exogenous bone marrow preparations in injured brain of the bone marrow recipient, and 2) determine if bone marrow-derived cells develop into functioning neurons and glial cells after HI injury. In this proposal we will deliver the HI injury to female mice on the seventh postnatal day. At eight weeks of age, they will undergo irradiation and receive bone marrow transplants from male mice of the same strain, some transgenic for Green Fluorescent Protein (GFP). The cells for transplantation will be prepared as crude marrow, marrow stromal cells or hematopoietic stem cells. The animals will be sacrificed at intervals after the transplant for immunohistochemical assessment of the male (Y chromosome) and GFP cells resulting in brain, followed by electrophysiologic testing of the GFP cells. This proposal satisfies the aims of the R21 model. We plan to obtain preliminary data for a future proposal which will deal with methods of enhancing bone marrow-derived cells in brain. Also, the proposal undertakes the novel use of a neonatal injury model, with the animals treated at a later age. This approach mimics what would occur in a clinical situation.